Flotation system



Jan. 7, 1934 J. w. scHLUTER FLOTATION SYSTEM Filed Aug. 21, 1958 llllUnited States Patent CQ,

3,117,082 Patented Jan. 7, 1964 3,117,082 FLOTA'I'ION SYSTEM .lohn W.Schluter, Maapequa, N .Y., assignor, by mesne assignments, to PfaudlerPermutt, Inc., Rochester, N.Y., a corporation of New York Filed Aug. 21,1953, Ser. No. 756,483 2 Claims. (Cl. 21h-221) This invention relates toflotation systems such as used for purification of 'liquids andseparation of suspended materials from liquids.

Flotation systems are in general well known and 4the generalconstruction and operating characteristics of ota- `tion apparatus andmethods to which the present invention may be applied are described, forexample, in Schluter application Serial No. 663,105, tiled April 2,1958, now U.S. Patent 2,994,432, for Control for Flotation SeparationSystems, and also Iuell Patent No. 2,330,589, granted September 28,1943, and Baum Patent No. 2,746,605, granted May 22, 1956. In suchsystems, .the influent liquid is generally processed from chemicals toprecipitate or coagulate dissolved or suspended material which is thenseparated from the liquid by floating it to the surface as a scum oriioc which is removed as by means of skimming paddles. The aeration ofthe liquid is generally accomplished after the chemical treatment andafter the lloc particles have formed to a considerable extent, and it isfound that the aeration of the liquid and more particularly itsdischarge through the valving employed in introducing it into theflotation chamber cause objectionable shearing of the iioc, reducing theparticle size and thus impeding the otation action. It is an object yofthe invention to lessen such shearing of partially formed floc.

In prior systems, the inuent liquid generally proceeds through allelements of the apparatus employed in a continuous manner and at thesame rate for each element, so that the rate of tlow of material intoand out of a lloc forming chamber, an aerating element and the tloationchamber, will all be the same. Under these conditions, it is diiicult tomaintain maximum efliciency and it is an object ofthe present inventionto permit variation in rate of iiow through one element of the system ascompared to another.

In many applications, the concentration of solids in the inuent materialmay vary quite widely from time to time and the oation eiciency may varyaccordingly. It is a further object of the invention to permitregulation of the dilution of the material being treated in theilotation chamber.

In the apparatus and method according to the present invention,clarified liquid is circulated to and from the dotation chamber at asuitable rate, is preferably aerated during this recirculation, theiniluent stream of liquid to be treated and in which the lloc has beenpartially formed being mixed with the circulating claried and aeratedliquid at an appropriate point and under relatively quiet conditions,thus achieving protection of partially formed iloc from shearing,control over the aeration and flotation steps of the process in a mannernot hitherto obtainable.

A system embodying the invention in a preferred form will now bedescribed with reference to the accompanying drawing, and the featuresforming the invention will then be pointed out in the appended claims.

In the drawings:

FIG. 1 is a schematic diagram of a system embodying the invention in apreferred form; and

FIG. 2 is an enlarged sectional view of the ilotation chamber inletcompartment where the iniiuent stream and recirculated, clarified liquidare mixed.

The elements of the system in general may be conventional and comprise areceiving tank or settling basin 1, to which the inuent liquid issupplied and from which it is 'taken by a pump 2 and delivered throughpipe 3 to aoc forming 4tank 4. Supply lines 5 and 6 equipped withrotometers, as indicated, discharge liquid from chemical lfeed tanks 7and S into the line 3, thus into tank 4. Each of the tanks 7 and 8 isequipped with liquid pump valves and agitator, as indicated, and it willbe understood that alum, ferrie sulphate or any other desired:precipitating or coagulating chemical may be mixed with water in thesetanks and then supplied at regulated rate by means of pumps and, asindicated, by the rotometers. Tank 4 may be vertically elongated, asindicated, and equipped with a vertical shaft 10 carrying paddles 1-1which are rotated at a slow rate by motor v12 so as to stir the liquidwithin the tank but without appreciable agitation or vertical movement,so that the iloc will gradually .form in Vthe liquid as it proceeds fromthe bottom to the top of tank 4 where it is discharged through supplyline 13 leading to the flotation chamber.

As is apparent, the operation of the elements justvdescribed may beregulated for optimum iloc formation and economy chemical treatment bythe influent liquid. Pipe 13 discharges into the inlet box orcompartment 14 of 'the flotation chamber or separator from which liquidiows over a Weir 15 into the ilotation chamber proper. The constructionof this chamber may be in general conventional and will be describedherein only to the extent necessary for an understanding of the presentinvention.

Claried water is withdrawn through an outlet 16 and the sludge floatingto the top of the liquid is removed by a paddle chain 17, beingdischarge at 18. The specific construction of the tank element may beselected as desired, structures such as shown and described in theapplication and patents above mentioned as well as elsewhere beingsuitable. In addition to being discharged through the outlet 16,clarified liquid is taken from the lower part of the flotation tank orseparator through the .pipe 20 controlled by a valve 21 and leadingthrough a gas and liquid mixing -unit 22 to pipe 23 which connects tothe intake of circulating -pump 24 which, in turn, discharges throughpipe 25 into a retention tank 26 from which recirculated liquid isdischarged through valve 27 and pipe 28 to the inlet box or compartmentof the flotation tank, where the recirculated stream from pipe 28 liscombined with the influent liquid from pipe 13 as shown most clearly inFIG. 2. As there shown, pipe 13 vterminates in a Vbaffle plate 30adjacent the bottom 31 of the inlet box flowing radially outward fromunder this `baffle plate, as indicated by the arrows. Immediately below.pipe 13 is a second and similar baille plate 32 attached by posts 33 tothe plate 30, and against which the recirculated clarified liquid frompipe 2S discharges so that this liquid also flows in a radiallyv outwardmanner between plate 30 and the bottom 31 of the inlet box. As isapparent, the recirculated liquid from pipe 28 and the influent liquidfrom pipe 13 are thus combined together and mixed thoroughly withoutappreciable agitation being involved in the mixing process.

The recirculated liquid is aerated by means of a system such as shown inFIG. l. As there shown, part of the discharge of pump 24 is by-passedback through a line 35 which connects two branches 36 and 37 which arevalved, as indicated, and contain air and liquid venturi jet pumps 3Sand 39 for mixing air into the recirculated liquid, which is thensupplied to the mixer 22 and thus introduced into the stream ofrecirculating liquid in pipe 23. The air injectors 38 and 39 aresupplied with air through piping 40 equipped with a rotometer and Valveas indicated for controlling the extent of aeration. Normally, only oneof the air injectors 38 or 39 will be used at any given time, the otherbeing shut oit by means of the indicated valves.

The retention tank may be of the type shown in the Baum patent abovereferred to and will provide for the dissolving in the recirculatedliquid of large quantities of air and generally several times the amountof air that can be held in solution at atmospheric pressure. Thereafter,as the recirculated liquid is discharged into the inlet box 14, aircommences to go out of solution so that the mixture from pipes 13 and 28is thoroughly aerated and without material destruction of any partiallyformed lloc. The flotation proceeds in the usual manner but withmarkedly increasing etlciency due to the obtaining and maintaining offloc particles of optimum size.

The method and apparatus of the invention may be used with flotationsystems of any known type, as, for example, systems used for clarifyingpaper mill waste, waste Water from canneries and slaughter houses, wastewater from railroad yards or any of a variety of processed liquids suchas sugar melts in sugar refineries. The purposes involved may includethe recovery of the suspended solids, the purication of the liquid foruse or further processing, or the purication of the liquid to permitdischarge into a stream or concentration of the solids to permiteconomical disposal thereof. As is apparent, the process of theinvention may be preceded or followed by any desired settling or otheroperations designed to assist in clarication or separation or performother operations on the liquids involved.

The quantity of clarified liquid which is recirculated to and from theotation chamber may be varied to suit particular conditions and may be,according to conditions, a fraction or a multiple of the quantity ofinfluent material supplied. For example, where the quantity of solidsinvolved is reasonably constant but the amount of liquid varies so thatthe inuent is supplied at a lower volumetric rate with a higherconcentration of solids at certain times, the recirculation `rate may becomparatively high resulting in a dilution of the influent as it entersthe flotation tank, wherever such dilution contributes to eliciency ofoperation. Since the rate of aeration and the rate of liquidrecirculation are independent within reasonable limits, the aeration mayalso be controlled substantially independently of the recirculationrate. In general, it is possible by controlling the recirculation rateas compared to the rate of inuent supplied and the aeration of therecirculated liquid so as to obtain maximum eiliciency in the airllotation action with minimum shearing or breaking up of the floc whichhas been formed prior to the influent reaching the inlet box. In themethod of the invention, it may be noted that the iniluent afterchemical treatment and partial formation of flot: may be brought to theinlet box and discharged therein without any substantial agitation ofany kind as, in the example illustrated, by means of a simple gravityflow and thus creating a very desirable condition by comparison withprevious systems in which a release of pressure is generally involvedresulting in great turbulence and a violent shearing action which tendsto destroy the partially formed floc.

What is claimed is:

1. In a flotation separating system, a dotation chamber, means forsupplying inlluent liquid containing suspended floatable material to thesaid chamber, means for removing clarified liquid and floated sludgefrom the said chamber, and means for withdrawing clarified liquid fromthe ilotation chamber, aerating it and mixing it with the influentliquid prior to introducing the same into the flotation chamber, inwhich the last said means comprises pipes for the two liquids havingtheir ends in opposed spaced relation for discharging the respectiveliquids in opposite directions, a baffle member positioned between thetwo pipe ends in spaced relation thereto and separating the streams ofliquid discharged therefrom, a pair of spaced plates surrounding thedischarge ends of the said pipes and forming a ilow passage for liquiddischarged by the said pipes against the said baffle, whereby the twostreams of liquid are diverted by the baille into the said flow passageand mixed together under relatively quiescent conditions.

2. In a otation separating system, a lloc-forming chamber, a dotationchamber having an inlet box, means for supplying inuent liquid from theHoc-forming chamber to the inlet box, means for removing clarifiedliquid and floated sludge from the flotation chamber, and means forwithdrawing claried liquid from the flotation chamber, aerating it andmixing it with the influent liquid from the lloc-forming chamber in thesaid inlet box, in which the last said means comprises pipes for the twoliquids having their ends in opposed spaced relation for discharging therespective liquids in opposite directions, a baille member positionedbetween the two pipe ends in spaced relation thereto and separating thestreams of liquid discharged therefrom, a pair of spaced platessurrounding the discharge ends of the said pipes and forming a flowpassage for liquid discharged by the said pipes against the said baille,whereby the two streams of liquid are diverted by the baffle into thesaid ow passage and mixed together under relatively quiescentconditions.

'References Cited in the le of this patent UNITED STATES PATENTSFloat-Treat System Bulletin 54-82, by Chain Belt Company, Milwaukee,Wis.; received in Patent Oliice Oct. 1l, 1957.

1. IN A FLOTATION SEPARATING SYSTEM, A FLOTATION CHAMBER, MEANS FORSUPPLYING INFLUENT LIQUID CONTAINING SUSPENDED FLOATABLE MATERIAL TO THESAID CHAMBER, MEANS FOR REMOVING CLARIFIED LIQUID AND FLOATED SLUDGEFROM THE SAID CHAMBER, AND MEANS FOR WITHDRAWING CLARIFIED LIQUID FROMTHE FLOTATION CHAMBER, AERATING IT AND MIXING IT WITH THE INFLUENTLIQUID PRIOR TO INTRODUCING THE SAME INTO THE FLOTATION CHAMBER, INWHICH THE LAST SAID MEANS COMPRISES PIPES FOR THE TWO LIQUIDS HAVINGTHEIR ENDS IN OPPOSED SPACED RELATION FOR DISCHARGING THE RESPECTIVELIQUIDS IN OPPOSITE DIRECTIONS, A BAFFLE MEMBER POSITIONED BETWEEN THETWO PIPE ENDS IN SPACED RELATION THERETO AND SEPARATING THE STREAMS OFLIQUID DISCHARGED THEREFROM, A PAIR OF SPACED PLATES SURROUNDING THEDISCHARGE ENDS OF THE SAID PIPES AND FORMING A FLOW PASSAGE FOR LIQUIDDISCHARGED BY THE SAID PIPES AGAINST THE SAID BAFFLE, WHEREBY THE TWOSTREAMS OF LIQUID ARE DIVERTED BY THE BAFFLE INTO THE SAID FLOW PASSAGEAND MIXED TOGETHER UNDER RELATIVELY QUIESCENT CONDITIONS.